1. Field of the Invention
The present invention relates to a digital camera. More specifically, the present invention relates to a digital camera for taking a picture of an object by making a flash lamp perform a light-emission with a major light-emission amount and by exposing a picture taking means for a first period.
2. Description of the Prior Art
There was a conventional digital camera in which in a case where a luminance level of the object is lower than a desired luminance level, a luminance level of the object is calculated by making a flash lamp perform a preliminary light-emission, and the major light-emission amount of the flash lamp is calculated on the basis of the luminance level. More specifically, with referring to FIG. 13, in a case where a luminance level E0 without the light-emission of the flash lamp is lower than a desired luminance level Et, a luminance level Es is detected by making the flash lamp perform the preliminary light-emission, the major light-emission amount is calculated on the basis of a luminance level Es, and the flash lamp is light-emitted with the major light-emission amount, therefore, a shortage amount of the luminance level is supplemented.
However,in such a prior art, in a case where the object exists under a fluorescent lamp which generates a flicker, since the luminance level Es in the preliminary light-emission changes about 5% there was a problem in that it was difficult to precisely calculate the major light-emission amount. That is, in the prior art, though the shortage amount is divided by the luminance level Es whereby the major light-emission amount is calculated, if an exposure period in the preliminary light-emission is long, the luminance level Es is changed by an influence of the flicker, therefore, there was a possibility that the major light-emission amount drastically deviates.
Therefore, the principal object of the present invention is to provide a novel digital camera.
Another object of the present invention is to provide a digital camera capable of precisely calculating a major light-emission element of a flash lamp.
Further object of the present invention is to provide a digital camera capable of calculating a most suitable major light-emission element in a set mode.
According to the present invention, a digital camera for taking a picture of an object by making a flash lamp perform a major light-emission with a major light-emission amount and exposing a picture taking means for a first period comprises: a detection means for detecting a luminance signal from a camera signal outputted from the picture taking means; an evaluation means for evaluating the luminance signal and outputting a luminance evaluation value; a first control means for exposing the picture taking means without a light-emission of the flash lamp; a second control means for making the flash lamp perform a preliminary light-emission with a preliminary light-emission amount and exposing the picture taking means for a second period shorter than the first period; and a calculation means for calculating the major light-emission amount on the basis of a first non-emission luminance evaluation value outputted from the evaluation means in response to a control of the first control means and a preliminary light-emission luminance evaluation value outputted from the evaluation means in response to a control of the second control means.
The first control means exposes the picture taking means without the light-emission of the flash lamp, therefore, the first non-emission luminance evaluation value is obtained from the evaluation means. The second control means makes the flash lamp perform the preliminary light-emission with the preliminary light-emission amount, and exposes the picture taking means for the second period, therefore, the preliminary light-emission luminance evaluation value is obtained from the evaluation means. The calculation means calculates the major light-emission amount on the basis of the first non-emission luminance evaluation value and the preliminary light-emission luminance evaluation value. The flash lamp is light-emitted with the major light-emission amount, and the picture taking means is exposed for the first period at this time. In addition, the second period is defined to be shorter than the first period.
In an aspect of the present invention, the first control means exposes the picture taking means for a third period. Then, a luminance evaluation value calculation means calculates a second non-emission luminance evaluation value in exposing the picture taking means for the first period without the light-emission of the flash lamp, on the basis of the first period, the third period and the first non-emission luminance evaluation value. Furthermore, a major light-emission amount calculation means calculates the major light-emission amount on the basis of the second non-emission luminance evaluation value, a target luminance evaluation value, the preliminary light-emission luminance evaluation value and the preliminary light-emission amount.
In an embodiment of the present invention, an exposure period calculation means calculates a most suitable exposure period in which the target luminance evaluation value is obtained without the light-emission of the flash lamp, on the basis of the third period, the first non-emission luminance evaluation value and the target luminance evaluation value. If the most suitable exposure period Is shorter than a longest exposure period which is a longest period capable of exposing the picture taking means, a cancellation means cancels the major light-emission. That is, since the target luminance evaluation value is obtained without the major light-emission, the cancellation means cancels the major light-emission.
According to the present invention, since an exposure period in the preliminary light-emission is defined to be shorter than the exposure period in the major light-emission, the preliminary light-emission luminance evaluation value is not influenced by an external light, therefore, it is possible to precisely calculate the major light-emission amount.
According to the present invention, a digital camera for taking a picture of an object by making a flash lamp perform a major light-emission with a major light-emission amount and by exposing a picture taking means comprises: a mode setting means for setting one of a first mode and a second mode; a first weighting amount table in which first weighting amount data is stored; a second weighting amount table in which second weighting amount data is stored; a detection means for detecting a luminance signal from a camera signal outputted from the picture taking means; a weighting means for weighting the luminance signal with a table corresponding to a set mode; a calculation means for calculating an output of the weighting means and outputting a luminance evaluation value; a first control means for making the flash lamp perform a preliminary light-emission and exposing the picture taking means; and a first computing means for computing the major light-emission amount on the basis of a preliminary light-emission luminance evaluation value outputted from the calculation means in response to an operation of the first control means.
The first control means makes the flash lamp perform the preliminary light-emission and exposes the picture taking means, whereby the camera signal is outputted from the picture taking means. When the first mode is set by the mode setting means, the weighting means weights the luminance signal included in the camera signal with the first weighting amount table. Furthermore, when the second mode is set by the mode setting means, the weighting means weights the luminance signal included in the camera signal with the second weighting amount table. The output of the weighting means is calculated by the calculation means, and the fist computing means computes the major light-emission amount on the basis of the preliminary light-emission luminance evaluation value outputted from the calculation means.
In an aspect of the present invention, the second control means exposes the picture taking means without the light-emission of the flash lamp, and the weighting means selects the first weighting amount table at this time. Then, a second computing means computes a most suitable exposure period in which a target luminance evaluation value is obtained without the light-emission of the flash lamp, on the basis of a second luminance evaluation value outputted from the calculation means in response to an operation of a second control means.
In the first mode, the most suitable exposure period is compared with a longest exposure period which is a longest period capable of exposing the picture taking means, if the most suitable exposure period is shorter than the longest exposure period, the major light-emission is cancelled. In addition, the first mode is an automatic light-emission mode in which the major light-emission is performed in response to the most suitable exposure period, and the first weighting amount data in a surrounding portion of the object is smaller than the first weighting amount data in a center portion of the object and larger than xe2x80x9c0xe2x80x9d.
In the second mode, the most suitable exposure period and the longest exposure period are compared with each other, if the most suitable exposure period is shorter than the longest exposure period, the most suitable exposure period is held as an exposure period in the major light-emission, and if the most suitable exposure period is equal to the longest exposure period or longer than the longest exposure period, the longest exposure period is held as the exposure period in the major light-emission. In addition, the second mode is a forced light-emission mode for making the flash lamp perform the major light-emission without respect to the most suitable exposure period, and the second weighting amount data has a value of xe2x80x9c0xe2x80x9d in the surrounding portion of the object.
According to the present invention, since the table is changed in response to the set mode, it is possible to calculate the most suitable major light-emission amount for the mode.
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.